Use the D-I-O-C Strategy:

When describing a picture use these types of sentences:

1- Use Describing sentences (what you can see)
2- Use Inferential sentences (what you think is there or is happening)
3- Opinions (give personal opinions about what you see)
4- Concluding sentence (you can finish your description with a conclusion)

Note: on the video they recommend a certain number of sentences for every type, but that is only useful for the activity they are preparing. In a normal picture description activity, simply use all these types of sentences, trying to use the description sentences the most and using the other types to expand and improve your description. Of course, the Concluding Sentence can only be one, and used to finish your description.

Examples:

1- Descriptions: This is a sandy beach
2- Inference: It is probably a weekend as it is packed with people
3- Opinion: I think the lady should accompany the little boy to the water because it can be dangerous
4- Conclusion: In my opinion this is a good example of what beaches have become today, a place to make money from tourists where it is difficult to enjoy and relax anymore.

Some Dos and Donts

DOS (things you should do)

- Use the present tense (simple or continuous) to talk about the picture they give you.
   
    It is a sunny day. The water is calm. Some children are playing on the beach.

- Use adjectives and adverbs to better describe things and actions.

    The beach is sandy and nice. There is a tall fat man sitting under a colourful umbrella.

- Speak clearly and in complete sentences (Subject + verb + objects/complements). Speak slowly if you are not very fluent, but don't stutter, break your speech or speak in a way which is difficult to understand. Speaking fast is not the important thing, the most important thing is speaking clearly and correctly.

DON'TS (things you should not do)

- Do not name characters in picture (unless everybody knows their names)

     John is kicking a ball on the sand and playing with Mary. (it sounds strange unless you and the examiner both know those people)

- Do not say: "On the right/left hand corner..."

     Well, I don't agree with this, using that once may show a good level of English, but because it is a construction long and complicated, you shouldn't use it more than once or maybe twice.

- Do not say: "I can see...", instead say: "A boy is.../ The children are.../The weather looks...".

     Again, I don't agree. It is ok to say "I can see..." when you start describing a picture and maybe a few times during your description. It is true that many people use this phrase many times, even all the time, and that really sounds terrible. Try to use a variety of expressions and don't repeat the same expression too many times. The more you vary, the higher level you show.